Rolling bearing device for a road-wheel, a method of manufacturing the same and a turning apparatus for a bearing member

ABSTRACT

In a rolling bearing device for a road-wheel including an inner shaft  1  that is provided with, on its outer-side end  10 , a flange  4  on which a road-wheel member mounted, and an outer ring  2  disposed around the inner shaft  1 , the inner shaft has, on its outer side, a hair-line pattern portion  5  that is formed by turning and that permits the manufacturing attribute of the bearing device to be identified based on the difference in the form of hair lines so formed. This permits the manufacturing attribute of the bearing device to be identified after the bearing device is assembled in a vehicle body. Furthermore, the representation of the manufacturing attribute can be readily implemented during a manufacturing step.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of co-pending application Ser. No.11/791,515 filed on May 24, 2007 and for which priority is claimed under35 U.S.C. §120. application Ser. No. 11/791,515 is the national phase ofPCT International Application No. PCT/JP2005/021468 filed on Nov. 22,2005 under 35 U.S.C. §371 and which claims priority to Application Nos.2004-342585 and 2004-342586 filed in Japan on Nov. 26, 2004,respectively. The entire contents of each of the above-identifiedapplications are hereby incorporated by reference.

TECHNICAL FIELD

The present invention relates to a rolling bearing device for aroad-wheel (hereinafter, also referred to simply as a rolling bearingdevice) that is used for a hub unit or the like loaded in an automotivevehicle, a method of manufacturing the same and a turning apparatus fora bearing member.

BACKGROUND ART

Conventionally known rolling bearing devices for road-wheels on whichroad wheels of automotive vehicles or the like are mounted include onewhich has an inner shaft that is provided with, on its outer-side end, aflange on which the road wheel is mounted; and has an outer ringdisposed around the inner shaft. The outer ring is fixed to a member ofa vehicle body, whereby the rolling bearing device is assembled in thevehicle body.

By the way, the completed rolling bearing devices may be stored inwarehouses, put in the stage of distribution or assembled in finalproducts to be introduced on the market. If, in such cases, inspectionsor replacements of the rolling bearing device are necessary for variousreasons, it is crucial to confirm the manufacturing attribute of therolling bearing device in question, or to confirm the serial number orlot number, and the numerical quantity thereof.

In this connection, characters representing the date of manufacture andthe like of the rolling bearing device may be die-stamped on a part ofthe surface thereof, thus offering information on the manufacturingattribute of the rolling bearing device. A rolling bearing wherein thecharacters for the identification of the manufacturing attribute thereofare represented on a bearing surface by die-stamping may be exemplifiedby one disclosed in Japanese Unexamined Patent Publication No.2003-222146 (FIG. 1).

On the other hand, a vehicular hub unit may be constituted by a rollingbearing device including: a hub wheel (inner shaft) as a shaft body towhich a road wheel, a disc rotor of a disc brake gear and the like aremounted; and a rolling bearing mounted on an outer periphery of the hubwheel for supporting the hub wheel. As disclosed in Japanese UnexaminedPatent Publication No. 2001-162338, for example, such a rolling bearingdevice is constituted as follows. A cylindrical end of theabove-mentioned hub wheel is radially outwardly bent and deformed, so asto be caulk-fixed to an axial end face of an inner ring of theabove-mentioned bearing, whereby the end face of the inner ring isaxially pressed for preventing the bearing from disengaging from the hubwheel.

Specifically, as shown in FIG. 9, the conventional rolling bearingdevice of this type includes: an outer ring member 101 which has a pairof outer raceways 101 a, 101 b and is fixed to the vehicle body side; ahub wheel 102 which includes an inner raceway 102 a opposing the outerraceway 101 a and allows the road wheel to be mounted to avehicular-outer-side end thereof; an inner ring member 103 which isfitted on a vehicular-inner-side end of the hub wheel 102 and on whichan inner raceway 103 a opposing the outer raceway 101 b is formed; androlling elements 104, 105 which are constituted by balls rollablyinterposed between a respective pair of outer raceways 101 a, 101 b andinner raceways 102 a, 102 b in an opposing relation.

The inner ring member 103 is prevented from disengaging from the hubwheel 102 by means of a caulked portion 102 b formed by bending anddeforming a cylindrical end of the hub wheel 102 in a radially outwarddirection.

In the conventional rolling bearing device, a cover 106 is pressed intoan inner periphery of a vehicular-inner-side of the outer ring member101 in order to increase muddy water resistance. A vehicular-inner-sideopening of the bearing device is sealed by the cover 106. On the otherhand, a vehicular-outer-side opening of the bearing device is sealed bya seal member 107 interposed between the outer ring member 101 and thehub wheel 102.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

It is expected that quite a large number of man-hours is required forquality control in a case where information items related to amanufacturing history (including measured data) of a product among themanufacturing attributes are not systematically managed.

Such a problem may be solved to some extent, for example, by preparing asheet for one product, which carries information such as theabove-mentioned manufacturing history. However, such a management on a“sheet-per-product” basis is not realistic because this managementsystem is cumbersome and requires a large-scale facility.

The bearing disclosed in Japanese Unexamined Patent Publication No.2003-222146 further has the following drawback. Once the bearing isassembled in a device and disposed in an innermost area of the device,it may be difficult to confirm the attribute of the bearing deviceafterwards. There is another problem that an area where the charactersare die-stamped is rusted as the bearing device is used for a long time,so that the die-stamped characters may become unreadable if they are sosmall. Some products provided with the die-stamped characters may carryonly information on the date of manufacture and the size. This may leadto a fear that a substantial length of time is taken to identify theabove-mentioned manufacturing attribute. In short, the die-stamped markfalls short of ensuring an exact and quick trace of the product.

In the above-mentioned rolling bearing device for a road-wheel includingthe inner shaft and the outer ring, it may be contemplated, for example,to die-stamp the characters on a back side of the flange of the innershaft, which is opposite to a side to which a road-wheel side member ismounted. Unfortunately, however, this back side of the flange isdirected inwardly in a state where the rolling bearing device isassembled in the vehicle body. Therefore, it is impossible to visuallyconfirm the die-stamped characters from outside. In a case where thecharacters are die-stamped on the bearing surface, another machine isrequired for performing an additional step of die-stamping thecharacters after the manufacture of the outer ring member or the innerring member, or after the fabrication of the bearing. This results in aproblem that increased labor and time is taken.

On the other hand, it has been a conventional practice for bearingmanufacturers to inspect the rolling bearing device including thecaulked portion, as shown in FIG. 9, by using, for example, a phototubeor the like, in order to determine whether the caulked portion 102 b isformed properly or not.

As shown in FIG. 9, however, the conventional rolling bearing device, asdescribed above, has the cover 106 pressed into the inner periphery ofthe outer ring member 101 in a manner to cover the caulked portion 102b. Once the cover 106 is mounted, therefore, the cover 106 must beremoved to confirm the existence or nonexistence of the caulked portion102 b. This makes it difficult to check the caulked portion 102 b. Alsobecause the caulked portion 102 b and the cover 106 are disposed on avehicular inner side after the conventional rolling bearing device isassembled in the vehicle, it is never easy to determine on the existenceor nonexistence of the caulked portion 102 b.

In view of the foregoing problems, it is the first object of theinvention to provide a rolling bearing device for a road-wheel whichfacilitates a post-assembly confirmation of the manufacturing attributethereof and which permits a manufacturing step to readily implement therepresentation of the attribute. It is also the first object of theinvention to provide a rolling bearing device for a road-wheel whichprovides an easy trace of a product shipped from factory and an easyidentification of a lot number or a serial number of the relevantproduct if inspections or replacements thereof are necessary and thelike, and which permits the quality control thereof to be accomplishedby a small man-hour, as well as to provide a turning apparatus for abearing member, which is capable of enhancing the traceability of therolling bearing device in this manner.

It is the second object of the invention to provide a rolling bearingdevice for a road-wheel which permits the existence or nonexistence ofthe caulked portion to be easily checked even when the cover is somounted as to cover the caulked portion, as well as to provide a methodof manufacturing the same.

Means for Solving the Problems

According to the invention for achieving the above-mentioned firstobject thereof, a rolling bearing device for a road-wheel comprises: aninner shaft that is provided with, on its outer-side end, a flange onwhich a road-wheel side member is mounted; and an outer ring disposedaround the inner shaft, and is characterized in that the inner shafthas, on its outer side, a hair-line pattern portion that is formed byturning and that permits a manufacturing attribute of the bearing deviceto be identified based on the difference in the form of hair lines soformed.

According to the rolling bearing device for a road-wheel constituted asdescribed above, the hair-line pattern portion exists on the outer sideof the inner shaft so that after the rolling bearing device is assembledin a vehicle body, the representation of the hair-line pattern portioncan be readily confirmed from outside in a state where the bearingdevice stays assembled in the vehicle body, without dismounting therolling bearing device from the vehicle body. That is, if thecorrelation between forms of the hair-line pattern portions andcharacters is previously defined and a hair-line pattern portioncorresponding to characters to be represented is formed on an outer-sidesurface of the inner shaft, the contents of the representation(characters) can be read by checking the hair-line pattern portionlater. Therefore, the rolling bearing device for a road-wheel can beenhanced in the traceability of the manufacturing attribute includingthe date of manufacture, processing conditions and the like.

As another advantage, the hair-line pattern portion is formed byturning. Hence, the hair-line pattern portion can be formed in parallelwith the turning of the inner shaft.

It is also preferred that the hair-line pattern portion is formed on aninternal surface of a guide cylinder which is disposed at an inner sideportion of the flange and serves as a guide during mounting theroad-wheel side member to the flange. This constitution is advantageousin the following sense. After the vehicle is completed, themanufacturing attribute of the rolling bearing device can be readilyacquired by removing a wheel of the road wheel as the road-wheel sidemember from the flange of the rolling bearing device. Furthermore, theguide cylinder suffers less rust production on the internal surfacethereof because the infiltration of water from outside is suppressed.Accordingly, the hair-line pattern portion can be maintained as it isover an extended period of time.

According to the invention for achieving the above-mentioned firstobject thereof, a turning apparatus for a bearing member comprises:turning condition processing means for deciding turning conditions of aturning tool according to information about a manufacturing attribute ona bearing member and generating a tool operation control signal based onthe turning conditions; and turning tool drive means for operating theturning tool according to the tool operation control signal provided bythe turning condition processing means, thereby implementing theinformation about the manufacturing attribute in a hair-line patternportion which is formed by turning the bearing member, and which permitsthe manufacturing attributes to be identified based on the difference inthe form of hair lines so formed.

According to the turning apparatus for a bearing member constituted asdescribed above, the hair-line pattern portion representing theinformation about the manufacturing attribute on the bearing member canbe automatically formed when the bearing member is formed by turning.Hence, the turning apparatus provides the_man-hour reduction. In short,the turning apparatus negates the need for an additional step ofimparting a product with a die stamp permitting the identification ofthe manufacturing attribute.

According to the invention for achieving the above-mentioned secondobject thereof, a rolling bearing device for a road-wheel whichcomprises: an outer ring; an inner ring member; rolling elementsarranged between the outer ring and the inner ring member; and a shaftbody having the inner ring member mounted to an outer periphery thereofand in which a caulked portion to be caulked to an axial end face of theinner ring member is formed at one end side of the shaft body, therebyfixing the inner ring member to the shaft body,

the bearing device is characterized in that the caulked portion iscaulked to the axial end face of the inner ring member by performing acaulking process in which a cylindrical portion formed at the one endside of the shaft body is radially outwardly bent and deformed by usinga predetermined caulking pressure acting from the one end side towardthe other end side of the shaft body, and in that identificationinformation indicating the existence of the caulked portion so formed isdie-stamped on a visually observable surface at the other end side ofthe shaft body by using the caulking pressure of the caulking process.

In the rolling bearing device for a road-wheel constituted as describedabove, the identification information indicating the existence of thecaulked portion so formed is die-stamped on the visually observablesurface at the other end side of the shaft body. Therefore, theexistence or nonexistence of the caulked portion can be readilydetermined from the die-stamped identification information, even if sucha cover as to cover the caulked portion is mounted to the one end sideof the shaft body. Since the identification information is die-stampedby using the caulking pressure of the caulking process, the die-stampingof the identification information in the above-mentioned surface can beaccomplished at the completion of the caulking process. This negates theneed for an additional step of die-stamping the identificationinformation.

It is preferred in the above-mentioned rolling bearing device for aroad-wheel that includes: at the other end side of the shaft body, aflange which is disposed in a concentric relation with the cylindricalportion at its one end and connected to a road-wheel side of a vehicle;and a socket part having a cylindrical portion which is disposed in aconcentric relation with the cylindrical portion and pressed against theroad-wheel side at its outer periphery and a bottom portion which isenclosed by the cylindrical portion, and that the identificationinformation is die-stamped on a surface of the bottom portion.

In this case, the identification information die-stamped on the surfaceof the bottom portion provides the easy confirmation of the existence ofthe caulked portion so formed, even if the rolling bearing device isassembled in the vehicle by connecting the flange to the road-wheel sideof the vehicle and pressing the cylindrical portion against theroad-wheel side. What is more, the identification information isdie-stamped on the surface of the bottom portion and hence, legibleidentification information can be provided without impairing theflatness or the like of the flange.

According to the invention for achieving the above-mentioned secondobject thereof, a method of manufacturing a rolling bearing device for aroad-wheel including: an outer ring; an inner ring member; rollingelements arranged between the outer ring and the inner ring member; anda shaft body having the inner ring member mounted to its outerperiphery,

the method comprises a caulking step of radially outwardly bending anddeforming a cylindrical portion formed at one end side of the shaft bodyby using a predetermined caulking pressure acting from the one end sidetoward the other end side of the shaft body, thereby forming a caulkedportion caulked to an axial end face of the inner ring member, and ischaracterized in that identification information indicating theexistence of the caulked portion so formed is die-stamped on a visuallyobservable surface at the other end side of the shaft body by using thecaulking pressure during the caulking step.

In the method of manufacturing the rolling bearing device for aroad-wheel constituted as described above, the identificationinformation indicating the existence of the caulked portion so formed isdie-stamped on the visually observable surface at the other end side ofthe shaft body during the caulking step of forming the caulked portion.Therefore, even when the cover is mounted to the one end side of theshaft body so as to cover the caulked portion, the existence ornonexistence of the caulked portion can be readily determined from theidentification information die-stamped at the other end side of theshaft body without removing the cover. Furthermore, the die-stamping ofthe identification information in the above-mentioned surface can beaccomplished at the completion of the caulking process. This negates theneed for the additional step of die-stamping the identificationinformation so that the man-hours of manufacturing the rolling bearingdevice can be reduced. Thus is prevented the increase in cost of thebearing device.

In the above-mentioned method of manufacturing the rolling bearingdevice for a road-wheel, an identification information imparting jig fordie-stamping the identification information can be pressed against thevisually observable surface during the caulking step.

In this case, the identification information imparting jig, as subjectedto the above-mentioned caulking pressure during the caulking process,utilizes the caulking pressure for die-stamping the identificationinformation in the visually observable surface. This permits thecaulking process including the operation of die-stamping theidentification information to be carried out in a more stable manner andbesides, the legible identification information can be die-stamped byefficiently using the caulking pressure.

It is preferred in the above-mentioned method of manufacturing therolling bearing device for a road-wheel that the identificationinformation is constituted by manufacturing information specific to therolling bearing device.

In this case, the manufacturing information specific to the rollingbearing device is also used as the above-mentioned identificationinformation, so as to negate the need for separately die-stamping theidentification information and the manufacturing information. Thus isreduced the man-hours of manufacturing the rolling bearing device.Furthermore, the management of the usage history of the rolling bearingdevice and the like can be facilitated because the manufacturinginformation specific to the rolling bearing device is die-stamped.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical sectional view showing a rolling bearing device fora road-wheel according to the first embodiment of the invention;

FIG. 2 is a group of diagrams each illustrating a hair-line patternportion;

FIG. 3 is a diagram explanatory of a turning apparatus for a bearingmember according to one embodiment of the invention;

FIG. 4 is a sectional view showing a rolling bearing device for aroad-wheel according to the second embodiment of the invention;

FIG. 5 is a sectional view showing an essential part of theabove-mentioned rolling bearing device in a state where a caulkedportion shown in FIG. 4 is yet to be formed;

FIG. 6 is a sectional view showing the essential part of theabove-mentioned rolling bearing device during the caulking step forforming the above-mentioned caulked portion;

FIG. 7( a) is a plan view showing an identification informationimparting jig shown in FIG. 6, and FIG. 7( b) is a sectional view takenon the line VIIb-VIIb in FIG. 7( a);

FIG. 8 is a sectional view showing the essential part of theabove-mentioned rolling bearing device at the time of completion of theabove-mentioned caulking step; and

FIG. 9 is a sectional view showing a conventional rolling bearingdevice.

BEST MODES FOR CARRYING OUT THE INVENTION

The embodiments of the invention will hereinafter be described withreference to the accompanying drawings.

FIG. 1 is a vertical sectional view showing a rolling bearing device fora road-wheel according to the first embodiment of the invention. Therolling bearing device for a road-wheel can be used for a road wheel ofa vehicle such as an automotive vehicle. The rolling bearing deviceincludes: an inner shaft 1 that is provided with, on its outer-side(outside) end 10, a flange 4 on which a road-wheel side member ismounted; and an outer ring 2 disposed around the inner shaft 1. Theroad-wheel side member (not shown) mounted to the flange 4 includes awheel of the road wheel and a brake rotor for disc brake.

An inner ring member 14 is fitted on an inner-side (inside) end 11 ofthe inner shaft 1. The outer ring 2 is disposed as fitted on the innershaft 1 and the inner ring member 14 via two rows of rolling elements 3a, 3 b.

The flange 4 of the inner shaft 1 is radially outwardly extended fromthe outer-side end 10 of the inner shaft 1. A mounting surface 4 a for aroad-wheel side member, defining an axially outer side of the flange 4,is so turned as to form a plane orthogonal to a shaft center C of thebearing. On the inner-side end 11 of the inner shaft 1, a small diameterportion 7 on which the inner ring member 14 is fitted is formed. Anannular stepped surface (butt surface) 8 is formed on an axially outerside of the small diameter portion 7. An intermediate diameter portion 9is extended axially outwardly from an outer rim of the stepped surface8. A great diameter portion 12 is formed on the further axiallyoutwardly from the intermediate diameter portion 9. The great diameterportion 12 defines a seal surface for a seal member 13 interposedbetween the inner shaft 1 and the outer ring 2.

The inner ring member 14 is mounted to the inner shaft 1 as fitted onthe small diameter portion 7 which is formed on the inner-side end 11 ofthe inner shaft 1 and butted against the stepped surface 8. That is, aninner periphery of the inner ring member 14 is in contact with an outerperiphery of the small diameter portion 7, while an axially outer sideend of the inner ring member 14 is butted against the stepped surface 8.Furthermore, the inner ring member 14 is impressed from the axiallyinner side toward the axially outer side by means of a caulked portion15 that is formed by expanding radially outwardly an outer side portionof the inner-side end 11 of the inner shaft 1. Thus, the inner ringmember 14 is fitted and fixed on the inner shaft 1 by way of an axialforce.

One raceway for the first rolling element 3 a is formed on an outerperiphery of the inner ring member 14, whereas one raceway for thesecond rolling element 3 b is formed on an outer periphery of theintermediate diameter portion 9 of the inner shaft 1. The first andsecond rolling elements 3 a, 3 b may also be tapered rollers rather thanthe balls shown in FIG. 1.

The outer ring 2 is disposed in a coaxial relation with the inner shaft1 and includes a cylindrical portion 16 and a flange 17. Two lines ofraceways for the first and second rolling elements 3 a, 3 b are formedon an inner periphery of the cylindrical portion 16. The flange 17 isdisposed on an outer peripheral side of the cylindrical portion 16. Theflange 17 is connected with a vehicle-body side member, whereby thisrolling bearing device for a road-wheel is fixed to a vehicle body. Whenthe rolling bearing device is fixed to the vehicle body, therefore, theflange 4 side of the inner shaft 1 is located on an outer side, whereasthe inner ring member 14 side fitted on the inner shaft 1 is located onan inner side.

A guide cylinder 6 is further formed on the outer-side end 10 of theinner shaft 1. The guide cylinder 6 is a cylindrical member that ismounted on a radial inner side portion of the flange 4 and serves as aguide when the road-wheel side member is mounted to the flange 4. Theguide cylinder 6 in FIG. 1 includes a cylindrical portion 18 formed onthe outer-side end of the inner shaft 1 in a manner to project axiallyoutwardly from the mounting surface 4 a of the flange 4. The guidecylinder 6 is formed integrally with the inner shaft 1. Therefore, aninternal surface 6 a of the guide cylinder 6 defines a closed-endcylindrical portion constituted by an inner periphery 19 of thecylindrical portion 18 and a bottom face 20 defining the axiallyinnermost side thereof.

A process of manufacturing the inner shaft 1 is briefly described. Amaterial is forged into an interim product having a predetermined shape,and the interim product is turned with a lathe turning machine.Subsequently, the inner shaft 1 is obtained by heat treating andpolishing the predetermined places of the interim product. Theabove-mentioned guide cylinder 6 is finished when the interim product isformed by turning. That is, the internal surface 6 a of the guidecylinder 6 is a turned surface which is finished not by polishing butonly by turning.

The rolling bearing device for a road-wheel of the invention includes ahair-line pattern portion 5 for identifying the manufacturing attributeof the rolling bearing device. In other words, the manufacturingattribute is represented by the hair-line pattern portion 5. Thehair-line pattern portion 5 is provided at a part of an outer-sidesurface of the inner shaft 1. The hair-line pattern portion 5 is formedby turning and enables the manufacturing attribute to be identifiedbased on the difference in the form of hair lines thus formed.

Specifically, the correlation between the form of the hair-line patternportion 5 formed on the outer side of the inner shaft 1 and the contents(characters) of the manufacturing attribute is previously defined suchthat the hair-line pattern portion 5 corresponding to the contents ofthe manufacturing attribute to be represented may be formed on the outerside surface of the inner shaft 1. Thus, the represented contents of themanufacturing attribute can be read by confirming the hair-line patternportion 5 later. The hair-line pattern portion 5 formed by turningconstitutes the surface finished by turning but not subjected to anyfurther machining (polishing). That is, the differences between thepatterns of the finished surface on the outer side of the inner shaft 1provide for the identification of the manufacturing attribute. Themanufacturing attribute represented by the hair-line pattern portion 5include the information on the manufacturing history (including measureddata) of a product, a serial number or a lot number thereof, and anumerical quantity thereof. The manufacturing history of the rollingbearing device includes, for example, the date of manufacture, workingconditions, a line number of a manufacturing plant and the like. Theterm “serial number”, as used herein, means each different numberassigned to each product, whereas the term “lot number”, as used herein,means each number assigned to each group of plurality of productsmanufactured at a predetermined plant in a predetermined period of time.Some rolling bearing devices may be assigned with the lot number as wellas the serial number, while the others may be assigned with only the lotnumber.

The position where the hair-line pattern portion 5 is formed A isdescribed specifically. The hair-line pattern portion 5 is preferablyformed on the internal surface 6 a of the guide cylinder 6 formed at theradially inner side portion of the flange 4 of the inner shaft 1. Thatis, the hair-line pattern portion 5 can be formed on the inner periphery19 of the guide cylinder 6, on the bottom face 20 thereof, or on both ofthe inner periphery 19 and the bottom face 20 thereof.

The hair-line pattern portion 5 is formed when the internal surface 6 aof the guide cylinder 6 is formed by turning. The form of hair lines canbe varied by, for example, varying the roughness of the hair lines byvarying the feed speed of a turning tool; by temporarily suspending thefeed of the turning tool; or by feeding the turning tool as keeping thetool from making contact with the internal surface 6 a of the guidecylinder 6 during the finish-machining. Specifically, if the turningtool is fed as keeping the tool from making contact with the internalsurface 6 a of the guide cylinder 6, discontinuous hair lines areformed. Thus, various patterns of the hair lines of can be formed on theinternal surface 6 a of the guide cylinder 6 in parallel with theturning of the internal surface 6 a of the guide cylinder 6. The hairlines are formed in a circumferential direction centered on the shaftcenter C (in a spiral form on the inner periphery 19 and in a verticalform on the bottom face 20) on the internal surface 6 a of the guidecylinder 6. The hair-line pattern portion 5 extends in a directionorthogonal to the above circumferential direction.

As shown in FIG. 2( a) and FIG. 2( b), for example, various hair-linepatterns can be formed by varying the width of the hair lines, the pitchthereof and the like with respect to the tool feeding direction (arrowe). It is noted that the drawings each depict an extracted part ofpredetermined circumferential width from the inner periphery 19 of theguide cylinder 6 on which the hair-line pattern portion 5 is formed,wherein the hair lines are circumferentially running.

In FIG. 2( a) and FIG. 2( b), a range m represents an area having thehair lines (or on which widely spaced hair lines are formed), whereas arange n represents an area free from hair lines (or on which finelyspaced hair lines are formed). The hair-line pattern portion 5 may alsobe varied by varying the infeed quantity of the tool.

In a case where the date of manufacture is provided as the manufacturingattribute, for example, the hair-line pattern portion 5 is formed asfollows. Referring to FIG. 1, the hair-line pattern portion 5representing the “year” of the date of manufacture is formed, rangingfrom an open end of the inner periphery 19 of the cylindrical portion 18of the guide cylinder 6. Subsequently, the hair lines representing the“month” are formed, ranging from the innermost area of the innerperiphery 19 of the cylindrical portion 18 to an outer side portion ofthe bottom face 20. Thereafter, hair lines representing the “day” areformed on an inner side portion of the bottom face 20. Since thehair-line pattern portion 5 is formed by turning, the hair-line patternportion 5 is defined by circumferential lines. Therefore, if a part ofthe hair-line pattern portion 5 should be rusted and become lesslegible, the other part of the circumferential lines permits theidentification of the attribute.

Next, the turning apparatus for turning the inner shaft 1 as the bearingmember constituting the rolling bearing device for a road-wheel shown inFIG. 1 and for forming the hair-line pattern portion 5 which permits theidentification of the manufacturing attribute on its inner shaft 1 isdescribed. As the turning apparatus, a lathe turning machine (not shown)normally used for turning the inner shaft 1 can be used. Furtherreferring to FIG. 3, the turning apparatus of the invention includes: aturning condition processing means 21 for controlling the operation ofthe turning tool of the lathe turning machine; and a turning tool drivemeans 22 for automatically operating the turning tool. The turningcondition processing means 21 can be constituted by a computing unit(computer) capable of storing the inputted information and the processedinformation and of performing an arithmetic processing on the variousinformation items. The turning tool drive means 22 can be constituted bya motor for moving the turning tool according to a signal from theturning condition processing means 21, and an actuator such as atransmission.

The turning condition processing means 21 includes a storage portion 23for storing the information on the manufacturing attribute on a bearingmember to be subjected to the turning process. The information on themanufacturing attribute is inputted from an external source and can beexemplified by the manufacturing history including the date ofmanufacture of the rolling bearing device, the working conditionsthereof, the line number of the manufacturing plant and the like. Theturning apparatus is disposed at a part of the manufacturing line forthe bearing member. The information on the manufacturing attribute on abearing member to be subjected to the turning process is automaticallyinputted from a managing computing unit (not shown) responsible for themanagement of the manufacturing line to the storage portion 23 of theturning condition processing means 21.

Alternatively, the information on the manufacturing attribute may beconstituted by the information possessed by the turning apparatusitself. That is, the information on the manufacturing attribute may beconstituted by the information possessed by the turning conditionprocessing means 21 of the turning apparatus, for example, theinformation on the date counted by the turning condition processingmeans 21 itself. The turning condition processing means 21 stores theinformation in the storage portion 23 thereof.

According to the information on the manufacturing attribute stored inthe storage portion 23, the turning condition processing means 21decides the turning conditions of the turning tool of the lathe turningmachine, and generates a tool operation control signal i based on theturning conditions so decided. More specifically, the previously definedcorrelation between the contents (characters) of the information on themanufacturing attribute and the form of the hair-line pattern portion 5to be formed on the inner shaft 1 is stored in the storage portion 23.An arithmetic processing portion 24 of the turning condition processingmeans 21 generates the tool operation control signal I, based on whichthe turning tool is so operated as to form the hair-line pattern portion5 corresponding to the contents of the information which is inputtedfrom the external source and is to be represented on the inner shaft 1.Meanwhile, a signal based on which the turning tool is operated to turnthe whole body of the inner shaft 1 is added to the tool operationcontrol signal i. The resultant signal is used for performing theturning process. That is, the hair-line pattern portion 5 is formed inparallel with the formation of the whole body of the inner shaft 1 byturning.

According to the tool operation control signal i supplied from theturning condition processing means 21, the turning tool drive means 22actually operates the turning tool so as to implement the information onthe manufacturing attribute in the desired hair-line pattern portion 5formed on the inner shaft 1. The position to form the hair-line patternportion 5 on the inner shaft 1 is limited to the internal surface 6 a ofthe guide cylinder 6. Thus, the represented contents (characters) of theinformation on the manufacturing attribute can be read by confirming thehair-line pattern portion 5 after the completed rolling bearing deviceis assembled in the vehicle body.

Now, means for confirming the hair-line pattern portion 5 thus formedare described. In a case where the hair-line pattern portion 5 is in asimple form, the contents of the manufacturing attribute may be acquiredby checking the hair-line pattern portion with eyes. In an alternativemethod, the illustration of which is omitted, it is also possible totake an image of the hair-line pattern portion 5 with camera and toprocess the image for identifying the hair-line pattern portion 5 basedon the shading or the white and black areas of the image. According tothis method, it is possible to identify the manufacturing attribute evenif the hair-line pattern portion 5 is in a complicated form. Besidessuch optical means, physical means may also be adopted to identify themanufacturing attribute based on the difference in surface roughness atthe hair-line pattern portion 5 or on the variation of the surfaceroughness.

According to the rolling bearing device for a road-wheel of theinvention, it is possible to enhance the traceability of themanufacturing attribute and to facilitate the trace thereof.Specifically, the manufacturing attribute, such as the manufacturinghistory, of the rolling bearing device can be readily identified in astate where the rolling bearing device rests assembled in the vehiclebody by removing only a wheel of the road wheel.

Furthermore, according to the turning apparatus of the bearing member ofthe invention, it is possible to form the hair-line pattern portion foridentifying the manufacturing attribute on the bearing member during theturning of the bearing member. Thereby it is possible to reduce themanufacturing man-hours.

Next, a rolling bearing device according to a second embodiment of theinvention and a method of manufacturing the same are described withreference to the drawings. The following description is one examplewhere the invention is applied to a hub unit for a driven wheel of avehicle.

FIG. 4 is a sectional view showing a rolling bearing device according toone embodiment of the invention. In the figure, the right-hand side is avehicular-inner side whereas the left-hand side is a vehicular-outerside (road-wheel side). The rolling bearing device 31 of the embodimentincludes a rolling bearing portion 32 of a double-row angular contactball bearing type. Specifically, the rolling bearing device 31 includes:an outer ring 33; an inner shaft (hub wheel) 34 as a shaft body; aninner ring member 35; and rolling elements 36, 37 constituted by aplurality of balls. The rolling bearing device 31 further includes:cages 38, 39 respectively retaining the rolling elements 36, 37circumferentially arranged with predetermined spacing; and a seal member40 interposed in space between the outer ring 33 and the inner shaft 34.

The above-mentioned outer ring 33 is a fixed bearing ring fixed to thevehicle body and double-row outer raceways 33 a, 33 b are formed on aninner peripheral side thereof. On the other hand, a rotary bearing ringis constituted by the inner shaft 34 and the inner ring member 35. Aninner raceway 34 a is formed at the place of the inner shaft 34 facingthe outer raceway 33 a such that the rolling element 36 can roll betweenthe inner raceway 34 a and the outer raceway 33 a. An inner raceway 35 ais formed at the place of the inner ring member 35 facing the outerraceway 33 b such that the rolling element 37 can roll between the innerraceway 35 a and the outer raceway 33 b. Thus, the rolling bearingdevice 31 of the embodiment constitutes the so-called third generationhub unit wherein an outer periphery of the inner shaft 34 constitutesone inner raceway 34 a of the double-row raceways.

A cylindrical portion extended axially is formed on a vehicular-innerside of the outer ring 33. A cover 41 of a closed-end shape for closingan interior of the bearing is pressed into an inner periphery 33 c ofthe cylindrical portion. In the rolling bearing device 31, the cover 41seals the annular opening between the inner and outer rings from thevehicular-inner side and, together with the above-mentioned seal member40 that seals the annular opening from the vehicular-outer side,prevents muddy water and foreign substances from entering the bearinginterior.

A flange 33 d extended radially outwardly is further formed on the outerring 33. A knuckle portion (not shown) included in a suspension systemof the above-mentioned vehicle is fixed to the flange 33 d by means of abolt (not shown) to be inserted through a bolt-hole 33 d 1 formedtherethrough.

A stepped portion 34 d is formed on a vehicular-inner side (one endside) of the inner shaft 34, and the above-mentioned inner ring member35 is fitted on the stepped portion 34 d. The inner ring member 35 isfixed to the inner shaft 34 by means of a caulked portion 34 e which isformed by a caulking step, to be described hereinafter, in which acylindrical portion formed at a distal end of the stepped portion 34 dis bent and deformed in a radially outward direction.

A socket part 34 b and a flange 34 c for mounting a road-wheel arefurther formed on a vehicular-outer side (the other end side) of theinner shaft 34. A plurality of hub bolts 42 for fixing a disc rotor of abrake system of the above-mentioned vehicle and the wheel (not shown) ofthe road wheel and the like are pressed and fixed onto the flange 34 c.

The above-mentioned socket part 34 b is open toward the vehicular-outerside. On the socket part 34 b, a cylindrical portion 34 b 1 to bepressed against the road wheel at its outer periphery; a ring-shapedbottom portion 34 b 2 surrounded by the cylindrical portion 34 b 1; anda concave portion 34 b 3 axially inwardly concaved from the bottomportion 34 b 2 are formed. The cylindrical portion 34 b 1, the bottomportion 34 b 2, the concave portion 34 b 3 and the flange 34 c aredisposed in a concentric relation with respect to the axial direction ofthe rolling bearing portion 32.

A ring-shaped axial end face of the bottom portion 34 b 2 is a surfacevisually observable from outside even when the rolling bearing device 31is assembled in the vehicle. Hence, this surface is provided with anidentification information representing portion 50. As will be describedhereinafter, the identification information indicating the existence ofthe caulked portion 34 e is on the identification informationrepresenting portion 50 by die-stamping (embossing) during a caulkingstep of forming the above-mentioned caulked portion 34 e.

Also referring to FIG. 5 to FIG. 8, the caulking step including adie-stamping operation for die-stamping the above-mentionedidentification information is described specifically.

In a preform A of the rolling bearing device prior to the caulking step,as shown in FIG. 5, the outer ring 33 and the inner ring member 35 whichboth are composed of a bearing steel or the like and the other bearingcomponents such as the rolling elements 36, 37 are assembled to theinner shaft 34. This inner shaft 34 is composed of a carbon steel (S55C)or a bearing steel or the like. A cylindrical portion 34 f for formingthe caulked portion 34 e is formed at one end side of the inner shaft34. The cylindrical portion 34 f is formed in a concentric relation withthe individual parts 34 b 1 to 34 b 3 of the socket part 34 b and theflange 34 c at the other end side of the inner shaft 34 with respect tothe axial direction of the rolling bearing portion 32. The one end sideand the other end side of the inner shaft 34 of the preform A are sopositioned as to be directed upwardly and downwardly respectively, asshown in FIG. 5. Then the preform A is subjected to the caulking stepusing a caulking jig 52 shown in FIG. 6.

In the caulking step as shown in FIG. 6, the caulking jig 52 is sopositioned as to be pressed against the above-mentioned cylindricalportion 34 f (FIG. 5). As indicated by the solid line and alternate longand two short dashes line in FIG. 6, the caulking jig 52 is brought intoa rolling motion as subjected to a predetermined caulking pressure Pacting from the one end side of the inner shaft 34 toward the other endside thereof, as indicated by the arrow in FIG. 6. Thus, the cylindricalportion 34 f is bent and deformed in the radially outward direction, soas to be caulked to an axial end face 35 b of the inner ring member 35whereby the caulked portion 34 e is formed.

In the caulking step, an identification information imparting jig 51which imparts the identification information indicating the existence ofthe caulked portion 34 e so formed is pressed against a surface of thebottom portion 34 b 2. The identification information imparting jig 51has the function of a holder jig for ensuring a stable execution of thecaulking step. A lower surface of the identification informationimparting jig 51 is positioned on a work table (not shown) and its uppersurface side is brought into contact with the surface of the bottomportion 34 b 2, so that the caulking step is carried out in a statewhere the surface of the bottom portion defines a surface receiving thecaulking pressure P at the other end side of the inner shaft 34. Theidentification information imparting jig 51 uses the caulking pressure Pto die-stamp the above-mentioned identification information on thesurface of the bottom portion 34 b 2.

In particular, also referring to FIG. 7, the identification informationimparting jig 51 includes: a column-shaped main body 51 a which isinserted in the cylindrical portion 34 b 1 of the socket part 34 b; andan imparting portion 51 b which is so provided as to project upwardlyfrom an upper face of the main body 51 a and which practically impartsthe identification information to the surface of the bottom portion 34 b2. The identification information imparting jig 51 is composed of amaterial (such as an ultrahard material) harder than the material of theinner shaft 34. The identification information imparting jig 51 uses thecaulking pressure P to (compress and) deform the bottom portion 34 b 2,and thereby embosses the identification information on the surface ofthe bottom portion.

The above-mentioned imparting portion 51 b includes a plurality ofdie-stamping parts 51 c for die-stamping a name of a bearingmanufacturer and a manufacturing lot number as the identificationinformation, for example. Marks exemplified by the alphabetic letters ornumerals constituting the above-mentioned manufacturer's name and suchare formed on the individual die-stamping parts 51 c. As illustrated byFIG. 7( b), the die-stamping part 51 c includes: an approximatefan-shaped base portion 51 c 1; and a die-stamping portion 51 c 2 whichis so provided as to project from the base portion 51 c 1 and whichdie-stamps a mark such as a corresponding numeral or the like by beingpressed into the bottom portion 34 b 2. In the die-stamping part 51 c,the base portion 51 c 1 thereof is removably mounted in a ring-shapedconcave portion 51 a 1 formed on an upper surface of the main body 51 a.Thus, it is possible to easily deal with the change of theidentification information such as the above-mentioned lot number.

When the caulking step is completed, at the one end side of the innershaft 34, the caulked portion 34 e is caulked to the axial end face 35 bof the inner ring member 35 as shown in FIG. 8, whereby the inner ringmember 35 is prevented from disengaging from the inner shaft 34 andwhereby the rolling bearing portion 32 is prevented from falling off asapplied with a predetermined pre-load.

At the other end side of the inner shaft 34, the caulking pressure Pworks so that the imparting portion 51 b that includes the pluraldie-stamping parts 51 c and is pressed against the surface of the bottomportion 34 b 2 (FIG. 6) is brought into a state where the respectivedie-stamping portions 51 c 2 of the die-stamping parts 51 c are pressedinto the inside of the bottom portion 34 b 2 (FIG. 8). Thus, theidentification information is automatically formed on theabove-mentioned identification information representing portion 50 (FIG.4) at the same time as the formation of the caulked portion 34 e iscompleted.

According to the embodiment constituted as described above, theidentification information indicating the existence of the caulkedportion 34 e so formed is die-stamped on the visually observable surfaceof the bottom portion 34 b 2 on the other end side of the inner shaft(shaft body) 34. Therefore, the existence or nonexistence of the caulkedportion 34 e can be easily determined from the identificationinformation even when the cover 41 is mounted to the one end side of theinner shaft 34 so as to cover the caulked portion 34 e. In addition, theidentification information is automatically die-stamped under thecaulking pressure P at the same time as the caulking step is completed.Therefore, the man-hours of manufacturing the rolling bearing device canbe reduced by omitting an additional operation for die-stamping theidentification information and the increase in cost of the bearingdevice is prevented. It is also possible to omit the visual inspectionof the conventional example wherein the phototube is used to check forthe existence or nonexistence of the caulked portion 34 e.

According to the embodiment, as shown in FIG. 6, the bottom portion 34 b2 is disposed in a concentric relation with the cylindrical portion 34 fto which the caulking pressure P is subjected, and on the side to whichthe caulking pressure P is directed. The identification informationimparting jig 51 is pressed against the visually observable surface ofthe bottom portion 34 b 2 so as to display the identificationinformation on the identification information representing portion 50defined by the visually observable surface. Therefore, even when therolling bearing device 31 is assembled in the vehicle by connecting theouter periphery of the cylindrical portion 34 b 1 and the other sideface of the flange 34 c to the road wheel side of the vehicle, theexistence of the caulked portion 34 e so formed can be readily confirmedby visually checking the identification information representing portion50. The identification information imparting jig 51 serving as the jigfor receiving the caulking pressure P can be used to ensure that thecaulking step including the die-stamping operation for stamping theidentification information is carried out in a more stable manner. Inaddition, the identification information imparting jig 51 is capable ofefficiently using the caulking pressure P for clearly die-stamping theidentification information. What is more, the identification informationis die-stamped on the visually observable surface and hence, it is easyto determine the existence or nonexistence of the caulked portion 34 enot only in the manufacturing process of the rolling bearing device 31but also during the course of distribution or after the bearing deviceis assembled in a product.

In an alternative constitution to that of the above-mentionedembodiment, the identification information imparting jig including thering-shaped main body may be pressed against the axial end face of thecylindrical portion 34 b 1 of the inner shaft 34 or the other end sideface of the flange 34 c, and then the identification information may bedie-stamped on the axial end face or the other end surface by using thecaulking pressure P applied during the caulking step. However, it ismore preferred to die-stamp the identification information on thesurface of the bottom portion 34 b 2 as described above, because theidentification information on the surface of the bottom portion providesthe easy determination on the existence or nonexistence of the caulkedportion 34 e after the rolling bearing device 31 is assembled in thevehicle, because the influence of the die-stamping operation on theinner shaft 34 is minimized, and because the surface of the bottomportion affords a sufficient space for permitting a large number ofinformation items to be clearly die-stamped. In other words, in a casewhere the identification information is provided on the axial end faceof the cylindrical portion 34 b 1, the identification information may bedetrimentally implemented in marks too small to be readable because theaxial end face has a smaller area than the surface area of the bottomportion 34 b 2. In a case where the identification information isprovided on the other end side surface of the flange 34 c, the flatnessor roundness of the flange 34 may be impaired by the caulking pressure Pand the flange run-out or the like may result.

According to the embodiment, the above-mentioned identificationinformation is constituted by the_manufacturing information specific tothe rolling bearing device 31 as shown in FIG. 7. This permits one ofthe operations for separately die-stamping these information items to beomitted so that the die-stamping operation can be accomplished in onestep. Hence, the man-hours of manufacturing the rolling bearing device31 can be reduced. Since the manufacturing information specific to thebearing device is used as the identification information, theinformation enables it to trace (trace and manage) the manufacturinghistory including the manufacturer, the part number, the date ofmanufacture, the location of manufacture and the like of the rollingbearing device 31 as well as the usage history thereof including theoperating time and the like. Thus is provided the rolling bearing device31 featuring good traceability.

The above-mentioned description illustrates the case where the inventionis applied to the hub unit for the driven wheel of the vehicle, whereinthe hub unit is equipped with the rolling bearing of the double-rowangular ball bearing type. However, the invention is applicable to anyrolling bearing device in which the caulked portion is formed at the oneend side of the shaft body, and the inner ring member is fixed to theshaft body, and in which the identification information indicating theexistence of the caulked portion so formed is die-stamped on thevisually observable surface at the other end side of the shaft body.Accordingly, the bearing type including the type of rolling element, thenumber of provided rolling elements and such; the shape of the shaftbody including the provision of the flange and such; the provision ofthe cover; and the like are not limited to those described above.Specifically, the invention is applicable to a rolling bearing deviceconstituting a hub unit for a driving wheel of a vehicle. The inventionis also applicable to a bearing device employing a tapered roller as therolling element. The invention is further applicable to a rollingbearing device wherein a pair of inner ring members are fitted fixed onan outer periphery of the shaft body, as well as to a sensor-equippedrolling bearing device incorporating therein a sensor unit in which anobject member to be detected by a sensor is mounted to the rotarybearing ring side and the sensor is mounted to the cover.

The foregoing description illustrates the case where the identificationinformation imparting jig in which the die-stamping part including thedie-stamping portion projected from the main body surface is removablymounted in the ring-shaped concave portion formed in the main bodysurface is used to die-stamp the identification information on the innerside of the bottom portion at the other end side of the shaft body, sothat the identification information representing portion with thedie-stamped identification information is provided on the visuallyobservable surface of the bottom portion. However, the identificationinformation imparting jig of the invention may be anything that iscapable of die-stamping the identification information by using thecaulking pressure. Hence, the constitution, shape and the like of theabove-mentioned imparting jig are not limited to those described above.For instance, the identification information imparting jig may include adie-stamping portion concaved from the above-mentioned main bodysurface, such as to emboss the identification information and hence, theidentification information representing portion including the embossedidentification information may be provided.

According to the invention, the identification information indicatingthe existence of the caulked portion so formed is automaticallydie-stamped on the visually observable surface at the other end side ofthe shaft body in conjunction with the formation of the caulked portionat the one end side of the shaft body. Therefore, even in the cover isso mounted as to cover the caulked portion, it is easy to determine theexistence or nonexistence of the caulked portion.

1. A rolling bearing device for a road-wheel comprising: an inner shaftthat is provided with, on its outer-side end, a flange on which aroad-wheel side member is mounted; and an outer ring disposed around theinner shaft, wherein the inner shaft has, on its outer side, a hair-linepattern portion that is formed by turning and that permits amanufacturing attribute of the bearing device to be identified based onthe difference in the form of hair lines so formed.
 2. The rollingbearing device for a road-wheel according to claim 1, wherein thehair-line pattern portion is formed on an internal surface of a guidecylinder which is disposed at an inner side portion of the flange andserves as a guide during mounting the road-wheel side member to theflange.
 3. A turning apparatus for a bearing member comprising: turningcondition processing means for deciding turning conditions of a turningtool according to information about a manufacturing attribute on abearing member and generating a tool operation control signal based onthe turning conditions; and turning tool drive means for operating theturning tool according to the tool operation control signal provided bythe turning condition processing means, thereby implementing theinformation about the manufacturing attribute in a hair-line patternportion which is formed by turning the bearing member, and which permitsthe manufacturing attribute to be identified based on the difference inthe form of hair lines so formed.
 4. A rolling bearing device for aroad-wheel which comprises: an outer ring; an inner ring member; rollingelements arranged between the outer ring and the inner ring member; anda shaft body having the inner ring member mounted to an outer peripherythereof and in which a caulked portion to be caulked to an axial endface of the inner ring member is formed at one end side of the shaftbody, thereby fixing the inner ring member and the shaft body, whereinthe caulked portion is caulked to the axial end face of the inner ringmember by performing a caulking process in which a cylindrical portionformed at the one end side of the shaft body is radially outwardly bentand deformed by using a predetermined caulking pressure acting from theone end side toward the other end side of the shaft body, and whereinidentification information indicating the existence of the caulkedportion so formed is die-stamped on a visually observable surface at theother end side of the shaft body by using the caulking pressure of thecaulking process.
 5. The rolling bearing device for a road-wheelaccording to claim 4, wherein the rolling bearing device includes: atthe other end of the shaft body, a flange which is disposed in aconcentric relation with the cylindrical portion at its one end andconnected to a road-wheel side of a vehicle; and a socket part having acylindrical portion disposed in a concentric relation with thecylindrical portion and pressed against the road-wheel side at its outerperiphery, and a bottom portion enclosed by the cylindrical portion, andwherein the identification information is die-stamped on a surface ofthe bottom portion.